Helical coil spring arrangement

ABSTRACT

A coil spring arrangement comprising a plurality of helical coil springs and means for holding the springs in position. The springs are fixed on a common axis by at least one set of interconnected clamps arranged substantially on a common plane transverse to the common axis. Each of these clamps are provided with jaws forming an opening which follows the helical path of the particular coil spring to be gripped and means for tightening the jaws on this coil spring.

United States Patent Desy 1 Mar. 14, 1972 [54] HELICAL COIL SPRING FORElGN PATENTS OR APPLICATIONS ARRANGEMENT 1,023,345 1] 1958 Germany ..267/ 178 [72] Inventor: Jacques J. Desy, Bearsville, N.Y.

- Primary Examiner-James B. Marbert Rtro In ted,Wodt k,N.Y. [73] Asslgnee 0 n corpora o 5 0c Att0rney-Brumbaugh, Graves, Donohue 8: Raymond [22] Filed: Jan. 20, 1970 [21] Appl. No.: 4,191 1 ABSTRACT A coil spring arrangement comprising a plurality of helical coil [52] US. Cl ..267/ 179, 267/ 168 p ings and means for holding the springs in position. The [51] Int. Cl ..Fl6f 1/12 springs are fixed on a common axis by at least one set of inter- Field of Search connected clamps arranged substantially on a common plane 267/179, 135, 180; 287/ 189.35 transverse to the common axis. Each of these clamps are provided with jaws forming an opening which follows the helical [56] References cued path of the particular coil spring to be gripped and means for UNITED STATES PATENTS tightening thejaws on this 6011 spring. 166,178 7/1875 Wootten ..267/ 178 10 Claims, 11 Drawing Figures i i f Patented March 14, 1972 v 3,649,000

3 Sheets-Sheet 1 INVENTOR M 60058 J. DES) his ATTORNEYS Patented March 14, 1912 0 3,649,000

3 Sheets-Sheet 2 INVENTOR JACQUES J. DES) his ATTORNEYS HELICAL COIL SPRING ARRANGEMENT BACKGROUND OF THE INVENTION The present invention relates to an improved clamping arrangement for helical coil springs. More particularly, the present invention relates to an arrangement for clamping a plurality of helical coil springs of round section in coaxial relationship.

In the design of spring-borne or spring-connected components, anumber of techniques have been used in the prior art to provide either a rigid or a flexible joint where the spring engages the attached component.

In the instances where helical coil springs are used either in tension or compression, the arrangement for gripping the coil is usually quite simple: it is possible, for example, to provide a receptacle at each end of the coil when the coil is used in compression, or to loop the coil around a pin at each-end when used in tension.

Of the many possible configurations, however, none have been devised where permit a plurality of helical coils to be arranged and gripped on a common axis while eliminating any form of sliding or rubbing of the coil against the adjoining component.

- ln'most cases, also, the prior art spring clamping or retaining arrangements cannot be used when the spring is loaded alternately in tension and in compression.

The functional life of a spring, in terms of the number of flexing applications it will sustain without appreciable changes in properties such as spring rate and nominal dimensions, is primarily a function of the maximum stress level to which it is subjected. In many cases the worst stress occurs near the ends of the coil due to combined conditions of torsion, bending, bearing and stress concentration effects at the clamping or retaining areas. Since the fatigue at these points of greatest stress may be further aggravated by the usual rubbing or sliding mentioned above, coil springs which would normally have an acceptably extended useful life are subject toearly failure.

In certain applications coil springs are continuouslysubjected to a corrosive atmosphere which combines with the other factors noted above to decrease the useful life. Particularly when corrosion is coupled with sliding or rubbing of the coils and where the points of maximum stress are exposed to the atmosphere, the corrosion of the spring or springs can result in a substantial reduction in their functional life.

In some particular applications, it may also be desirable to minimize the overall friction of a spring system,'as required in certain oscillating devices operating at or near natural resonance. Both the external rubbing or sliding and the internal friction at points of increasedstress as found in spring systems employing the prior art gripping arrangements lead to an undue loss of energy which must be supplied to maintain the system in operation.

In certain applications, finally, it may also be desirable to adjust the overall active length of the spring assembly with great accuracy. In the oscillating devices mentioned above, such an adjustment is useful to preset the spring rate.- In other applications this adjustment may be required to accurately locate .the free end component with respect to the fixed end component attached to the spring.

SUMMARY OF THE INVENTION It is one object of the present invention, therefore, to provide a clamping arrangement for helical coil'springs which permits a substantial increase in the useful life of the spring system.

It is also an object of the present invention, to provide a coil spring arrangement which may be used alternately in tension or compression and which permits a substantial reduction in the internal and external friction (damping) of the system.

It is a still further object of the present invention to provide a clamping arrangement for helical coil springs which permits the active length of the springs to be adjusted with high accuracyu for minordifferences-between the shape ofthezclamp opening These, as wellas otherobjects which will become apparent l in the .discussion that follows, is-achieved' accordingto the present invention, by' providing a lpluralityof helical coil springs arranged on a common axisandat least one spring holding device having arplurality-of clampsarrangedsubstantially on a common plane transverse to the common axis of the springs. Each of'the clamps includes aset ofjaws forming an opening which follows the helical pathof'an associated one of the coil 'springsand means for-tightening the jaws on the as sociated coil spring.

If the coil springarrangementaccording-to.the present inof elastomeric material between the jawsofeach clamp and its associated coil. spring. Such a'liner iseffective tocompensate and the coil spring element.

Thus, the clamps which .are used in holdingx means according to the present invention-are provided-with anopening which is actuallyhelical in'shape. Because'theclampopenings follow the helical path of the coilspring's it' is-possible to grip the coil springs without creatingpoints-of-increased stress. Because the coil spring arrangement, according to the present invention, is provided with a plurality of helical coil springs arranged on a common axis, the spring load is divided and the stress placed on anywindividualspring substantiallyzreduccd. This reduction intspringstress. leads to. a corresponding increaseinthelife of the spring arrangement; Tests have shown that this spring arrangementmay besubjected toseveralbillion stress reversing. cycles --without *changing .IIS' natural frequency.

Because of the absence of slippageas'well as the low internal friction of the springs due to the-minimization 'ot:spring stress, the overall dampening of thegspringwarrangement according to the present invention is .very low, consisting-mainly of material hysteresis. The absence of rubbing vorsliding parts also results in extremely quiet operation.

The coil spring arrangement accordingto the-present inventionmay be used alternately in tension or compression. Because of the multiple coil configuration, it may also be used in applications requiring-relatively highzstiffness in thetlateral direction; For example, the coilspringarrangement may be used as thesolestructural support 'for'an oscillating mass attached'to one end thereofleven if the mass is moved backzand forth at or nearthe natural resonance :ofthe; spring system as is the case in applications. such aszelectromechanical linear mo- The spring holding device;-according tothe present invention, may be used as a means of tuning aspring+masssystem by effecting any desired incrementalchange in itseactive length. This may be accomplished by simply loosening theclamps'attached to'one end'of thecoil springs-and resetting-theI-effective vcoil arc length by rotation of the springs relative to the-clamps.

This technique of changing the 0. arc. length: mayealso' be used to I achieve great accuracy in the location zof. the componentsattached to the springholding devices.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1' is a=top view, partiallycut away andpartially in section, of a coil' spring arrangement accordingto afirst preferred embodiment-of thepresentinvention.

FIG. 2 is an elevational view, partially cut away and partially in section, of the embodiment of the invention illustrated in FIG. I. The sectional portions of FIG. 2 have been taken along the plane 22 in FIG. 1.

FIG. 3 is a bottom view of the embodiment of the invention illustrated in FIGS. 1 and 2.

FIG. 4 is a detailed view of a portion of the upper spring holding device illustrated in FIGS. I and 2, at the position of one of the spring holding clamps.

FIG. 5 is a detailed view of the central portion of the lower spring holding device illustrated in FIGS. 2 and 3.

FIG. 6 is a top view, partially cut away and partially in section, of a coil spring arrangement according to a second preferred embodiment of the present invention. The portion of FIG. 6 shown in section is taken along the plane 6-6 in FIG. 7.

FIG. 7 is an elevational view of the embodiment of the invention illustrated in FIG. 6.

FIG. 8 is a bottom view of the embodiment of the present invention illustrated in FIGS. 6 and 7.

FIG. 9 is a detailed view of a portion of the lower spring holding device illustrated in FIG. 7.

FIG. 10 is a top view, partially cut away, of a coil spring arrangement according to a third preferred embodiment of the present invention.

FIG. 11 is an elevational view, partially representational and partly in section, of the embodiment of the invention illustrated in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will now be described in connection with FIGS. 1-11 of the drawings. FIGS. 1-5 thereof illustrate a first embodiment, FIGS. 6-9 a second embodiment, and FIGS. 10 and II a third preferred embodiment of the present invention.

In the first preferred embodiment of the present invention, shown in FIGS. 1-5, four identical helical coil springs l, 2, 3 and 4 are concentrically nested and held in position by an upper ring-shaped and a lower cross-shaped holding device. The upper ring-shaped device 5 is provided with four clamps, 6, 7, 8 and 9 which grip the upper ends of the springs l, 2, 3 and 4, respectively. The ring 5 is provided with suitable holes 10 for convenient attachment to other components.

The lower cross-shaped holding device or spider II is provided with four clamps 12, 13, I4 and 15, to grip the lower ends of the coil springs l, 2, 3 and 4, respectively. In this embodiment the spider II is formed to two arms 16 and 17 which are joined together at the center by means of four bolts. Two of these bolts I8 and 19, arranged to pass through respective holes 20 and 2] in the arms 16 and 17, are shown in FIG. 5. These holes 20 and 21, as well as the other two holes 22 and 23 in the spider arms can also be conveniently used to permit attachment of other components. As an illustration, FIGS. 2, 3 and 5 show a laminated plunger assembly 24 attached to the spider I I such as that used in a resonating-type linear motor.

As noted above, each of the upper coil ends is provided with a respective clamps 6, 7, 8 and 9. These clamps are each tensioned by two screws 25 and 26 and press the wire of their associated coils against an inner clamp piece 27 arranged between the coil wire and the ring 5.

At each of the lower coil ends, the U-type tension clamps I2, l3, l4 and I5 engage the coil wire, compressing it against a grooved portion of the spider by means of two screws 28 and 29.

At both the upper and the lower coil ends, the coil mating surfaces formed by the clamps are helically contoured to form a nearly perfect fit with the helical shape of the spring wire.

In the second preferred embodiment of the present invention, shown in FIGS. 6-9, helically contoured holes are accurately generated by one-piece clamping or retaining components 30 and 31, formed integrally with the ring 5 and th spider II, respectively.

The helically contoured holes may be machined with a ball end-mill tilted to the helix angle of the mating coil, the work simultaneously rotating about and advancing along the helix center axis. The limit of through machining of such a configuration depends on the geometry. A coil engagement depth of better than one coil wire diameter is easily achieved in this manner with a wire diameter to coil outer diameter ratio of l/ 14.

To preload the clamps 30 and 3] in tension about the wire. a slot is cut in an extending portion of the clamp hoop. One side of the extending portion is provided with a threaded hole and the other side with a clearance hole so that a screw 32 may be properly installed and tightened to within a specified torquing range.

In either of the above two preferred embodiments the screws may induce sufficiently large deflections in the slot regions of the clamps to cause the screws to bend outwards when tightened. To avoid this difiiculty, the clamp surfaces bearing the screwheads (and washer and/or lockwasher) may be suitably machined at an angle slightly nonperpendicular to the hole axis so that the surface will become perpendicular to the screw axis as the screw reaches a specified preload.

The third preferred embodiment of the present invention is illustrated in FIGS. 10 and 11. In this embodiment only three helical coil springs 33, 34 and 35 are nested together about a common axis.

The third embodiment illustrates how a coil spring arrangement may be constructed to have relatively flexible clamping joints. Whereas the first and second preferred embodiments, described above, require only a single clamp at each end of each coil, the flexible joint configuration requires two similar clamps, 36, 37 and 38, 39 at each end of each coil. Each of the helically contoured holes through the clamps is larger than the coil wire diameter to permit engaging an elastomeric-type liner 40 between each coil and each clamp. The radial thickness of each liner 40 is preferably sufficient to provide a nominal 15 percent compression when the clamps are secured over the coils. Each joint thus acts as a semiflexible ball joint permitting each of the coils to flex freely therein within a small but effective range of motion in any direction. This type of coil spring arrangement has greater overall dampening characteristics than the all-metal embodiments but its performance in other respects is very similar. With due consideration for the different end-restraint factor, such a flexible doublejointed type spring arrangement usually will have about the same axial stiffness as an otherwise identical all-metal, singlejoint type embodiment having twice the effective coil arc length.

Corrosion protection may be provided in each of the three preferred embodiments described above, by constructing the spring arrangements of a suitable material. To reduce the cost of fabrication, the spring assemblies may be made of inexpensive materials and completely coated with an elastomeric-type material such as vinyl applied by the fluidized bed coating method.

It will be appreciated that various modifications and changes can be made in the coil spring arrangement of the present invention, in addition to those noted above, without departing from the essence of the present invention.

Iclaim:

l. A coil spring arrangement for flexibly coupling two mechanical members, said spring arrangement comprising, in combination:

a. a plurality of helical coil springs arranged on a common axis;

b. first spring holding means coupled to one of said members, having a plurality of first clamps arranged substantially on a common plane transverse to said common axis, each of said first clamps including:

l. jaws forming an opening which follows the helical path of one of said coil springs, and 2. means for tightening saidjaws on said one coil spring.

2. The spring arrangement defined in claim I, wherein said first spring holding means is arranged to hold said plurality of coil springs adjacent to the ends thereof.

3. The coil spring arrangement defined in claim 2, further comprising second spring holding means coupled to the other of said members and arranged to hold said plurality of coil springs adjacent to the other ends thereof, said second spring holding means having a plurality of second clamps arranged substantially on a common plane transverse to said common axis, each of said second clamps including:

1. jaws forming an opening which follows the helical path of one of said coil springs, and

2. means for tightening said jaws on said one coil spring.

4. The spring arrangement defined in claim 1, wherein said helical coil springs are of round section.

5. The spring arrangement defined in claim 1, wherein said first clamps further include liner means, made of elastomeric material, arranged to surround said one coil spring within said opening in said jaws, thereby to compensate for minor 'differences between the shape of said opening and said one coil spring.

6. The spring arrangement defined in claim 1, wherein said means for tightening said jaws includes at least one screw in threaded engagement with said jaws.

7. The spring arrangement defined in claim 1 wherein said first spring holding means is ring-shaped and said first clamps are distributed around the ring. a

8. The spring arrangement defined in claim 1, wherein said first spring holding means is star-shaped and said first clamps are arranged at the points of the star.

9. The spring arrangement defined in claim 3, wherein said first spring holding means is ring-shaped and said first clamps are distributed around the ring and said second spring holding means in star-shaped and said second clamps are arranged at the points of the star.

10. The spring arrangement defined in claim 1, wherein all of said coil springs have approximately the same diameter,

said coil springs being arranged in interleaved relationship about said common axis. 

1. A coil spring arrangement for flexibly coupling two mechanical members, said spring arrangement comprising, in combination: a. a plurality of helical coil springs arranged on a common axis; b. first spring holding means coupled to one of said members, having a plurality of first clamps arranged substantially on a common plane transverse to said common axis, each of said first clamps including:
 1. jaws forming an opening which follows the helical path of one of said coil springs, and
 2. means for tightening said jaws on said one coil spring.
 2. means for tightening said jaws on said one coil spring.
 2. The spring arrangement defined in claim 1, wherein said first spring holding means is arranged to hold said plurality of coil springs adjacent to the ends thereof.
 2. means for tightening said jaws on said one coil spring.
 3. The coil spring arrangement defined in claim 2, further comprising second spring holding means coupled to the other of said members and arranged to hold said plurality of coil springs adjacent to the other ends thereof, said second spring holding means having a plurality of second clamps arranged substantially on a common plane transverse to said common axis, each of said second clamps including:
 4. The spring arrangement defined in claim 1, wherein said helical coil springs are of round section.
 5. The spring arrangement defined in claim 1, wherein said first clamps further include liner means, made of elastomeric material, arranged to surround said one coil spring within said opening in said jaws, thereby to compensate for minor differences between the shape of said opening and said one coil spring.
 6. The spring arrangement defined in claim 1, wherein said means for tightening said jaws includes at least one screw in threaded engagement with said jaws.
 7. The spring arrangement defined in claim 1 wherein said first spring holding means is ring-shaped and said first clamps are distributed around the ring.
 8. The spring arrangement defined in claim 1, wherein said first spring holding means is star-shaped and said first clamps are arranged at the points of the star.
 9. The spring arrangement defined in claim 3, wherein said first spring holding means is ring-shaped and said first clamps are distributed around the ring and said second spring holding means in star-shaped and said second clamps are arranged at the points of the star.
 10. The spring arrangement defined in claim 1, wherein all of said coil springs have approximately the same diameter, said coil springs being arranged in interleaved relationship about said common axis. 